1. Field of the Invention
The present invention relates to a novel coating composition, the more preferable coating composition containing a dispersing component of an inorganic oxide sol prepared by a specific process for preparing, the specific process for preparing the dispersing component of the inorganic oxide sol, and the more preferable coating composition prepared by a specific process for preparing and the specific process for preparing the coating composition. More particularly, it relates a novel coating composition comprising a ceramic ingredient which gives paint film having excellent stain resistance, stain-removing property, weathering resistance, light resistance, chemical resistance, moisture resistance and appearance and is excellent in environment friendliness and safety. Further, it relates a process for preparing the coating composition and a process for preparing a dispersing component of an inorganic oxide sol used in the coating composition.
2. Background Information
In recent years, many oil droplets and dusts have existed in air by environmental changes such as air pollution. As the result, some problems have occurred, among which paint film on buildings, automobiles and the like are easier to be stained than former and it""s stain is difficult to remove. Thus, it has been desired that paint films have resistance to the stain, i.e. stain resistance and property to remove stain from stained paint films, i.e. stain-removing property. In such circumstances, it is desired to produce coating compositions which give paint films having excellent stain resistance, stain-removing property, weathering resistance, light resistance, gloss, appearance, water resistance and chemical resistance and is excellent in environment friendliness and safety property.
Convenient coating compositions having stain resistance which have been used, comprise a fluorine-containing resin as a main component. The stain resistance of the coating compositions is attributed to excellent weathering resistance of the fluorine-containing resin. The fluorine-containing resin manifest the performance by (1) stability caused by larger bond energy between fluorine atom and carbon atom compared with that between hydrogen atom and carbon atom and (2) water repellency and oil repellency caused by larger atomic radius of fluorine atom compared with that of hydrogen atom and lower surface free energy attributed to lower polarizability between fluorine atoms (0.68xc3x9710xe2x88x9224cc).
However, there are some problems that the fluorine-containing resin is restricted in the range of resin designation because of different polymerization reactivity compared with general acrylic monomers, attributed to stronger electronegativity of fluorine atom and expensive, and some fluorine-containing monomer is bad in solubility to solvents. Further, there is fear that bad influence to environment may be caused by the production of hydrogen fluoride at stage of waste disposal of the paint film comprising the fluorine-containing resin. Accordingly, though the fluorine-containing resin manifests excellent performance, these problems such as the restriction of cost and use and bad influence to the environment at the waste disposal have been highlighted.
A coating composition, which gives paint films having weathering resistance with an acrylic polyol produced by reacting a polymerizable monomer having stability to ultraviolet rays as essential component, is near recently suggested as a coating composition having excellent weathering resistance (Laid Open Japanese Patent Application Publication Hei 1-261409). But, there is no description about stain resistance in this publication. Also, a coating composition comprising a partial condensate of an organic silicon compound and a specific silica particulate as the coating composition having excellent stain resistance (Laid Open Japanese Patent Application Publication Hei 2-3468). But, there is no specific description about the resin component used in the coating composition in the publication. Further, a coating composition comprising an acrylic polyol resin, a binder, inorganic organo sol and a solvent is suggested (Laid Open Japanese Patent Application Publication Hei 4-173882). But, though the coating composition is improved in stain resistance, weathering resistance and light resistance a little, the coating composition has a defect that the stain-removing property is insufficient.
Thus, the coating composition, which gives paint films having stain resistance, stain-removing property, weathering resistance and light resistance, has been not developed.
The present invention accordingly has an object to provide coating compositions which give paint film having excellent stain resistance, stain-removing property, weathering resistance, light resistance, water resistance, chemical resistance, and appearance and are excellent in environment friendliness and safety property. Another object of the invention is to provide processes for preparing the coating compositions and processes for preparing a dispersing component of an inorganic oxide sol used in the coating compositions.
Extensive investigations undertaken by the present inventors to develop the coating composition having properties described above lead to a discovery that the objects can be achieved by a coating composition comprising a specific acrylic resin, a polyisocyanate compound or an aminoplast resin and a specific ceramic ingredient, that more excellent specified properties can be obtained by mixing the specific ceramic ingredient with the specific acrylic resin at a final stage of the polymerization process of the acrylic resin, and that most excellent specified properties can be obtained by using the ceramic ingredient treated with a specific silane coupling agent.
The present invention was completed on the basis of the discoveries described above.
Thus, the present invention provides a coating composition comprises (A) a resin having a glass transition temperature of 50 to 120xc2x0 C., a number average molecular weight of 2,000 to 100,000, a hydroxyl value of 50 to 150 mgKOH/g and an acid value of 1 to 25 mgKOH/g, which is produced by copolymerizing 10 to 90 percent by weight of (a) a (meth) acrylic acid ester of an alkyl alcohol of 1 to 12 carbon atoms, 10 to 50 percent by weight of (b) a polymerizable double bond-containing and hydroxyl group-containing monomer, 0.1 to 10 percent by weight of (c) a polymerizable double bond-containing and carboxyl group-containing monomer, 0 to 20 percent by weight of (d) styrene, 0 to 20 percent by weight of (e) acrylonitrile and 0 to 10 percent by weight of (f) other polymerizable double bond-containing monomer, (B) at least one compound selected from the group consisting of a polyisocyanate compound having two or more unblocked isocyanate groups and/or blocked isocyanate groups in the molecule and an aminoplast resin, (C) a dispersing component of at least one inorganic oxide sol selected from the group consisting of an aluminum oxide sol, a silica sol, a zirconium oxide sol and an antimony oxide sol, wherein an amount of a nonvolatile matter of the said ingredient (C) is 5 to 60percent by weight based on a total amount of nonvolatile matter.
Further, the present invention provides a process for preparing a coating composition which comprises copolymerizing 10 to 90 percent by weight of (a) a (meth) acrylic acid ester of an alkyl alcohol of 1 to 12 carbon atoms, 10 to 50 percent by weight of (b) a polymerizable double bond-containing and hydroxyl group-containing monomer, 0.1 to 10 percent by weight of (c) a polymerizable double bond-containing and carboxyl group-containing monomer, 0 to 20 percent by weight of (d) styrene, 0 to 20 percent by weight of (e) acrylonitrile and 0 to 10 percent by weight of (f) other polymerizable double bond-containing monomer to produce a resin (A) having a glass transition temperature of 50 to 120xc2x0 C., a number average molecular weight of 2,000 to 100,000, a hydroxyl value of 50 to 150 mgKOH/g and an acid value of 1 to 25 mgKOH/g, adding a dispersing component of at least one inorganic oxide sol (C) selected from the group consisting of an aluminum oxide sol, a silica sol, a zirconium oxide sol and an antimony oxide sol into a polymerization liquid containing the resin (A) in 5 to 60 percent by weight as nonvolatile matter based on a total amount of nonvolatile matter after finishing of the copolymerization of the resin (A) to produce a organic-inorganic composite, and then mixing at least one compound (B) selected from the group consisting of a polyisocyanate compound having two or more isocyanate unblocked groups and /or blocked isocyanate groups in the molecule and an aminoplast resin with the organic-inorganic composite.
Also, the invention provides a process for preparing a dispersing component of an inorganic oxide sol dispersed in a solvent which comprises dehydrating a dispersing component of an aqueous inorganic oxide sol by azeotropic distillation with an azeotropic solvent to water and then surface-treating the dispersing component with a silane coupling agent.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
Preferable embodiment for practicing the invention The resin used as the resin (A) in the coating composition of the invention has a glass transition temperature of 50 to 120xc2x0 C. When the glass transition temperature is less than 50xc2x0 C. , the obtained paint film has insufficient hardness and the paint film having excellent weathering resistance is difficult to obtain. When the glass transition temperature is more than 120xc2x0 C., the operation efficiency in coating process is bad and the obtained paint film is lower in appearance such as distinctness of image and gloss. The lower stain-removing property, which is a defect of the coating composition suggested in Laid Open Japanese Patent Applications Hei 4-173882, is improved by controlling the glass transition temperature in the range described above. Preferable glass transition temperature is in the range of 50 to 100xc2x0 C. in view of hardness, appearance and stain-removing property of the paint film and operation efficiency.
The resin has a number average molecular weight of 2,000 to 100, 000. When the number average molecular weight is less than 2,000, the obtained paint film has insufficient weathering resistance. When the number average molecular weight is more than 100,000, the operation efficiency is bad in coating process. The number average molecular weight of the resin (A) is preferably 2,200 to 70,000, more preferably 2,200 to 40,000 in view of weathering resistance of the paint film and operation efficiency.
The resin has a hydroxyl value of 50 to 150 mgKOH/g. When the hydroxyl value is less than 50 mgKOH/g, the obtained paint film has insufficient crosslinking density and the paint film having excellent stain resistance and excellent stain-removing property is difficult to obtain. When the hydroxyl value is more than 150 mgKOH/g, cracks in the paint film is easily caused because contraction stress become large by excessive density of the structure of the paint film at formation of the paint film and is impossible to be relaxed. The hydroxyl value is preferably in the range of 50 to 130 mgKOH/g in view of stain resistance, stain-removing property and the inhibition of cracks of the paint film.
The resin has an acid value of 1 to 25 mgKOH/g. When the acid value is less than 1 mgKOH/g, the dispersibility of pigments in an enamel paint system becomes bad so that objectionable points such as precipitation and aggregation of pigments are caused in storage of the coating composition. When the acid value is more than 25 mgKOH/g, the trend of the extreme decrease in the pot life of the coating composition is observed. The acid value is preferably 2 to 20 mgKOH/g in view of dispersibility of pigments, storage stability and pot life of the coating composition.
The resin of ingredient (A) is produced by copolymerizing essentially (a) a (meth) acrylic acid ester of an alkyl alcohol of 1 to 12 carbon atoms, (b) a polymerizable double bond-containing and hydroxyl group-containing monomer and (c) a polymerizable double bond-containing and carboxyl group-containing monomer, and optionally (d) styrene, (e) acrylonitrile and (f) other polymerizable double bond-containing monomer.
The (meth) acrylic acid ester of an alkyl alcohol of 1 to 12 carbon atoms (hereinafter called xe2x80x9cacrylic esterxe2x80x9d) of component (a) used as the essential monomer component is used in ratio of 10 to 90 percent by weight based on total weight of the all monomers. The acrylic ester is necessary and essential component to control the glass transition temperature of the paint film. When the alkyl group in the portion of the alcohol has carbon atoms of more than 12, the trend of the excess decrease in the glass transition temperature of the obtained resin is observed. When the amount of the acrylic ester is less than 10 percent by weight, it is impossible to control the glass transition temperature of the obtained resin in the range of not less than 50xc2x0 C. unless other monomers having lower polymerization reactivity are not used. If other monomers having lower polymerization reactivity are used, the weathering resistance of the paint film is decreased. Contrariwise, when the amount- of the acrylic ester is more than 90 percent by weight, the desired amount of hydroxyl groups and carboxyl groups is not introduced in the resin and the paint film having excellent weathering resistance, stain resistance and stain-removing property is difficult to obtain.
A Preferable amount of the acrylic ester is 35 to 80 percent by weight in order to obtain the paint film having desired and preferable properties.
The alkyl alcohol of 1 to 12 carbon atoms which constitute the acrylic ester of component (a) may be a straight chain alcohol, a branch chain alcohol or an alcohol having a cyclic alkyl group. Examples of acrylic esters of component (a) are, for example, methylmethacrylate, ethylmethacrylate, n-propylmethacrylate isopropylmethacrylate, n-butylmethacrylate, isobutylmethacrylate, t-butylmethacrylate, pentylmethacrylate, hexylmethacrylate cyclohexylmethacrylate 2 -ethylhexylmethacrylate adamantylmethacrylate, dodecylmethacrylate, isobornylmethacrylate, methylacrylate, ethylacrylate, n-propylacrylate, isopropylacrylate, n-butylacrylate , isobutylacrylate , t-butylacrylate , pentylacrylate, hexylacrylate, cyclohexylacrylate, 2 -ethylhexylacrylate adamantylacrylate, dodecylacrylate, isobornylacrylate. The acrylic esters may be utilized singly or as a combination of two or more members.
The polymerizable double bond-containing and hydroxyl group-containing monomer of component (b) used as essential monomer component is used in ratio of 10 to 50 percent by weight based on total weight of the all monomers. When the amount is less than 10 percent by weight, it is impossible to introduce crosslinking points needed in the obtained resin and to obtain the paint film having excellent weathering resistance, stain resistance and stain-removing property. On the other hand, when the amount is more than 50 percent by weight, the unreacted hydroxyl groups remain in crosslinking reaction between the obtained resin and ingredient (B). Therefore, the water resistance and the moisture resistance are decreased and the decrease of the weathering resistance of the paint film is caused. Further, the crosslinking density of the paint film is excessively increased. A preferable amount of the monomer of component (b) is 10 to 30 percent by weight in order to obtain the paint film having desired properties by introducing the proper number of crosslinking points in the resin.
The polymerizable double bond-containing and hydroxyl group-containing monomer of component (b) has each one or more polymerizable double bonds and one or more hydroxyl groups, preferably one polymerizable double bond and one hydroxyl group. Examples of the monomer of component (b) is, for example, hydroxyethylmethacrylate, hydroxypropylmethacrylate hydroxybutylmethacrylate, 1, 4 - butandiolmonomethacrylate, e-caprolactone adduct of hydroxyethylmethacrylate, ethylene oxide adduct of hydroxyethylmethacrylate, propylene oxide adduct of hydroxyethylmethacrylate, hydroxyethylacrylate hydroxypropylacrylate, hydroxybutylacrylate, 1, 4 -butandiolmonoacrylate, e-caprolactone adduct of hydroxyethylacrylate, ethylene oxide adduct of hydroxyethylacrylate, propylene oxide adduct of hydroxyethylacrylate. The monomers of component (b) may be utilized singly or as a combination of two or more members.
The polymerizable double bond-containing and carboxyl group-containing monomer is essentially used in ratio of 0.1 to 10 percent by weight based on total weight of the all monomers. When the amount is less than 0.1 percent by weight, the acid value of the obtained resin is excessively decreased, the dispersibility of pigments in an enamel paint system becomes bad and objectionable points such as precipitation and aggregation of pigments are caused in storage of the coating composition. When the amount is more than 10, the trend of the extreme decrease in storage stability and pot life of the coating composition is observed. The amount of component (c) is preferably 1 to 5 percent by weight, more preferably 1 to 3 percent by weight in view of dispersibility, storage stability and pot life of the coating composition.
The polymerizable double bond-containing and carboxyl group-containing monomer of component (c) has each one or more polymerizable double bonds and one or more carboxyl groups, preferably one polymerizable double bond and one or two carboxyl groups.
Examples of component (c) are, for example, methacrylic acid, acrylic acid, itaconic acid, mesaconic acid, maleic acid, fumaric acid, xcfx89-carboxy-polycaprolactone (n=2) monoacrylate (for example ALONIX M-5300, a product of TOA GOUSEI CHEMICAL INDUSTRY L.T.D.), phthalic acid monohydroxyethylacrylate (for example ALONIX M-5400, a product of TOA GOUSEI CHEMICAL INDUSTRY L.T.D.), acrylic acid dimer (for example ALONIX M-5600, a product of TOA GOUSEI CHEMICAL INDUSTRY L.T.D.). These may be used singly or as a combination of two or more members.
Styrene of component (d) is not essential component and is optionally used to improve appearance such distinctness of image of the paint film. When styrene is used, the amount of styrene is in ratio of not more than 20 percent by weight based on the total weight of all monomers. When the amount of styrene is more than 20 percent by weight, the trend of the decrease in the weathering resistance, stain resistance and stain-removing property of the paint film is observed. The amount of styrene is preferably 1 to 18 percent by weight in view of the balance of appearance such distinctness of image, weathering resistance, stain resistance and stain-removing property of the paint film.
Acrylonitrile of component (e) is not essential component and is optionally used to improve the adhesion of the paint film to a substrate and impact resistance. When acrylonitrile is used, the amount of acrylonitrile is in ratio of not more than 20 percent by weight based on the total weight of all monomers. When the amount of acrylonitrile is more than 20 percent by weight, the trend of the decrease in the weathering resistance, stain resistance and stain-removing property of the paint film is observed. The amount of acrylonitrile is preferably 1 to 18 percent by weight in view of the balance of the adhesion of the paint film to the substrate, weathering resistance, stain resistance and stain-removing property of the paint film.
Another polymerizable double bond-containing monomer of component (f) is not essential component and is optionally used according to substrates and the purpose of use in the designation of the paint film. When other monomer is used, the amount is not more than 10 percent by weight. When the amount of other monomer is more than 10 percent by weight, it is difficult to obtain the paint film having desired properties. The amount of other monomer of component (f) is preferably 1 to 7 percent by weight, when component (f) is used.
Another polymerizable double bond-containing monomer of component (f) has one or more polymerizable double bonds, preferably one polymerizable double bond.
Examples of other monomers of component (f) is, for example, PHOSMER (a product of UNICHEMICAL L.T.D.), glycydilmethacrylate, glycidylacrylate, allylmethacrylate, allylacrylate, 3,4 -epoxycyclohexylmethylmethacrylate 3,4 epoxycyclohexylmethylacrylate, phenylmethacrylate, phenylacrylate, a-methylstyrene, p-vinyltoluene, methacrylamide, acrylamide, N, N-dimethylmethacrylamide, N,N-dimethylacrylamide, methacrylic acid-1, 2, 2, 6, 6-pentamethyl-4-piperidinyl ester, acrylic acid-1, 2, 2, 6, 6- pentamethyl-4-piperidinyl ester, methacrylic acid-2, 2, 6, 6-tetramethyl-4 -piperidinyl ester, acrylic acid-2, 2, 6, 6-tetramethyl-4-piperidinyl ester ; aliphatic vinylethers such as ethylvinylether isopropylvinylether, n-propylvinylether, n-butylvinylether isobutylvinylether, 2-ethylhexylvinylether and cyclohexylvinylether 2, 3 - dihydrofuran, 3, 4 -dihydro-2H-pyran trimethoxysilylpropylmethacrylate, maleic anhydride, itaconic anhydride, maleic acid ester and fumaric acid ester. These may be utilized singly or as a combination of two or more members.
The resin of ingredient (A) is obtained by copolymerizing the monomers in the ratio described above. The polymerization method is particularly not limited. Various convenient polymerization methods such as solution polymerization in an organic solvent, suspension polymerization , emulsion polymerization, bulk polymerization and precipitation polymerization can be utilized. Also, the embodiment of the polymerization is particularly not limited. For example, radical polymerization, cation polymerization and anion polymerization can be utilized. Preferable the embodiment of the polymerization is radical polymerization in view of industrial point. Examples of polymerization initiators in radical polymerization are, for example, an organic peroxides such as t-butylhydroperoxide, cumenehydroperoxide, t-butylperoxyneodecanate, t-butylperoxypivalate, t-hexylperoxy-2 -ethylhexanoate, methylethylketoneperoxide; and an 4 azo initiators such as 2,2xe2x80x2-azobis (2,4-dimethylvaleronitrile), 2,2xe2x80x2-azobis (2-methylpropionitrile) (AIBN) and 2,2xe2x80x2-azobis (2-methylbutironitrile). Of course, other polymerization initiators than the above described polymerization initiators can be used. The polymerization initiators may be utilized singly or as a combination of two or more members.
The polymerization temperature is preferably 60 to 150xc2x0 C. in general. When the polymerization temperature is less than 60xc2x0 C., the radical polymerizaition initiators are difficult to be decomposed and the polymerization reaction is difficult to be proceeded. When the polymerization temperature is more than 150xc2x0 C., though the radical polymerizaition initiators are decomposed to generate radicals by heating, the life time of the radicals is short and a propagation reaction is difficult to be effectively proceeded. The polymerization time is indiscriminately not determined because of the influence of the polymerization temperature and the other conditions, but is generally sufficient at the level of 2 to 6 hours.
At least one compound selected from the group consisting of a polyisocyanate compound having two or more unblocked isocyanate groups and/or blocked isocyanate groups in the molecule and an aminoplast resin is used as a curing agent of ingredient (B) in the coating composition of the present invention.
Preferable examples of the polyisocyanate compounds having two or more isocyanate groups are, for example, compounds called xe2x80x9ciscyanate monomerxe2x80x9d such as hexamethylenediisocyanate isophoronediisocyanate tolylenediisocyanate diphenylmethanediisocyanate, xylylenediisocyanate and dicyclohexylmethan-4,4xe2x80x2-diisocyanate; and polyisocyanate derivatives such as biulet compounds , isocyanurate derivatives and trimethylolpropane adducts thereof. The polyisocyanate compound may be utilized singly or as a combination of two or more members.
The polyblocked isocyanate compound contains the compounds produced by blocking a part or all of the isocyanate groups in the polyisocyanate compounds described above with a blocking agent. Examples of the blocking agents, for example, e-caprolactam; a ketoxime blocking agents such as methylethylketoxime, methylisoamylketoxime and methylisobutylketoxime; a phenol blocking agents such as phenol, cresol, catechol and nitrophenol; an alcohol blocking agents such as isopropanol and trimethylolpropane; and an active methylene blocking agents such as malonic acid ester and acetoacetic acid ester. The polyblockedisocyanate compounds may be utilized singly or as a combination of two or more members.
Preferable examples of the aminoplast resins are melamine resin and guanamine resin. The aminoplast resins may be utilized singly or as a combination of two or more members. The aminoplast resins are not restricted as long as the aminoplast resins have two or more reactive groups in the molecule. Therefore, the melamine resin and the guanamine resin may have one or more triazine rings in the molecule. The reactive groups in the resins include preferably methylol group, imino group and an etherificated methylol group with methanol, butanol or the like.
In the coating composition of the present invention, ingredient (A) and ingredient (B) are formulated in the following ratio. When ingredient (B) is the polyisocyanate compound having two or more unblocked isocyanate groups and/or blocked isocyanate groups in the molecule, a mole ratio of unblocked isocyanate groups and/or blocked isocyanate groups in ingredient (B) to hydroxyl groups in ingredient (A) is preferably 0.6 to 1.6, more preferably 0.8 to 1.2. When the mole ratio is less than 0.6, a part of the hydroxyl groups in the resin of ingredient (A) may not react and remain in the crosslinking reaction of the polyisocyanate compound of ingredient (B) and the resin of ingredient (A), so that the water resistance and moisture resistance of the obtained paint film may decrease and further the weathering resistance of the paint film may cause by the decrease of the water resistance and moisture resistance. On the other hand, when the mole ratio is more 1.6, a part of unblocked isocyanate groups and/or blocked isocyanate groups may not react and remain. In such case, the water resistance and moisture resistance of the obtained paint film may decrease so that the weathering resistance of the paint film may decrease by the decrease of the water resistance and moisture resistance.
When ingredient (B) is the aminoplast resin, the weight ratio of the nonvolatile matter of ingredient (A) to ingredient (B) is preferably in the range of 97 : 3 to 60 : 40, more preferably in the range of 95: 5 to 65: 35, furthermore preferably in the range of 91: 9 to 70: 30. When the amount of the aminoplast resin is less than formulation ratio of 97: 3, the crosslinking density of the paint film is decreased and the desired properties such as solvent resistance of the paint film may not be obtained. When the amount of the aminoplast resin is more than formulation ratio of 60 : 40, objectionable points such as the decrease of flexibility of the paint film may be caused.
In the coating composition of the present invention, a dispersing component of at least one inorganic oxide sol selected from the group consisting of an aluminum oxide sol, a silica sol, a zirconium oxide sol and an antimony oxide sol is utilized as a ceramic ingredient of ingredient (C). The preferable inorganic oxide sol is a silica sol.
Many of the inorganic oxide sols are generally supplied as aqueous dispersing system. In the case of the aqueous dispersing system, when the coating composition is a waterborne system, the dispersing system can be utilized as it is. When the coating composition is a solution system of an organic solvent, the methods such as phase conversion into the organic solvent can be utilized. Preferable organic solvents include ketone solvents such as methylisobutylketone and cyclohexanone.
The method of phase conversion into the organic solvent includes the method that a water-soluble organic solvent is added into the aqueous dispersing component and a operation of distillation and removement of water is repeated to proceed the phase conversion into the desired organic solvent.
The dispersing component of a silica sol can be produced by adding silicon tetrahalide into water, by adding acid into aqueous sodium silicate solution and the like. Examples of commercial aqueous dispersing components are SNOWTEX-O (trade name, a product of Nissan Chemical Industries, Ltd.) and SNOWTEX-N (trade name, a product of Nissan Chemical Industries, Ltd. ). Examples of commercial organic solvent dispersing components are SNOWTEX-MIBK-ST (trade name, a product of Nissan Chemical Industries Co. Ltd.).
The dispersing component of an inorganic oxide sol is preferably a dispersing component of an inorganic oxide sol surface-treated with a silane coupling agent, more preferably a dispersing component of silica sol surface-treated with a silane coupling agent. The surface-treated dispersing component of an inorganic oxide sol can introduce various functional groups on the surface of the particles. Therefore, when the surface-treated dispersing component is used in the coating composition of the present invention, the surface-treated dispersing component easily bonds with organic components such, as the resin, the polyisocyanate compound or the aminoplast resin. In such case that the ceramic ingredient chemically bonds with the organic component, the crosslinking of the paint film is tighter than that without chemical bonds and the stain resistance, stain-removing property and weathering resistance are improved.
The silane coupling agents include vinyltrimethoxysilane vinyltriethoxysilane, xcex3-methacryloyloxypropyltrimethoxysilane, xcex3-glycidoxypropyltrimethoxysilane, xcex3-aminopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane and dimethyldimethoxysilane. The silane coupling agent is preferably methyltrimethoxysilane, dimethyldimethoxysilane, xcex3-glycidoxypropyltrimethoxysilane and xcex3-methacryloyloxypropyltrimethoxysilane, more preferably methyltrimethoxysilane and dimethyldimethoxysilane. Examples of commercial silane coupling agents are A-162, A-163 and AZ-6122 (each trade name, a product of NIPPON UNICAR CO., L.T.D.). The silane coupling agents may be utilized singly or as a combination of two or more members. When the dispersing component of the inorganic oxide sol is surface-treated with the silane coupling agent, the amount of the silane coupling agent is preferably 1 to 40 percent by weight, more preferably 5 to 30 percent by weight based on the nonvolatile matter of the inorganic oxide sol.
The dispersing component of the inorganic oxide sol surface-treated with the silane coupling agent is preferably a dispersing component of the inorganic oxide sol produced by dehydrating water contained in an aqueous inorganic oxide sol by azeotropic distillation with an azeotropic solvent to water and then surface-treating the dispersing component with the silane coupling agent. More preferably, the dispersing component of the inorganic oxide sol is a dispersing component of the silica sol. The dispersing component of the inorganic oxide sol produced by the method improves the stain resistance, stain-removing property and weathering resistance of the obtained paint film. Further, a coating composition having high nonvolatile matter can be easily obtained by preparing the coating composition because it is possible to increase the concentration of the inorganic oxide sol. Therefore, it is possible to select a thinner for controlling the viscosity of the coating composition from various thinners, in broad selection width and to increase the thickness of the paint film in coating.
The azeotropic solvents include a water-soluble alcohol, a water-soluble carboxylic acid ester and a water-soluble cyclic ether.
The water-soluble alcohols include ethanol, n-propylalcohol, i-propylalcohol, n-butylalcohol, i-butylalcohol, sec-butylalcohol, t-butylalcohol, methylcellosolve, ethylcellosolve ethyleneglycolmonomethylether, ethyleneglycolmonoethylether ethyleneglycolmono-n-propylether, ethyleneglycolmonobutylether diethyleneglycolmonomethylether, diethyleneglycolmonoethylether, diethyleneglycolmonobutylether, 3 -methyl-3 -methoxybutanol, propyleneglycolmonomethylether, ethyleneglycol and propyleneglycol.
The water-soluble carboxylic acid esters include methylacetate and ethylacetate. The water-soluble cyclic ethers include 1,4-dioxane.
The azeotropic solvents may be utilized singly or as a combination of two or more members.
A water-insoluble solvent also can be used together with a mediation of the water-soluble solvent in order to improve the efficiency of dehydration by azeotropic distillation. The water-insoluble solvents include benzene, xylene, toluene, cyclohexanone, diphenylether and dibutylether. The water-insoluble solvent may be utilized singly or as a combination of two or more members. The amount of the water-insoluble solvent is limited in the range in which the sol is not flocculated and generally preferably 1 to 10 percent by weight, though the amount is different according to the kind of the water-insoluble solvents.
The dehydration by azeotropic distillation is preferably proceeded with the dropping of azeotropic solvent. The dehydration by azeotropic distillation is proceeded in the range of preferably 30 to 100xc2x0 C., more preferably 40 to 80xc2x0 C. The dehydration by azeotropic distillation can be proceeded under reduced pressure or atmosphere, preferably under reduced pressure. The water content of the inorganic oxide sol dispersed in the azeotropic solvent after the dehydration by azeotropic distillation is generally preferably not more than 2 percent by weight, more preferably not more than 1 percent by weight. The concentration of the dispersing component of the inorganic oxide sol dispersed in the azeotropic solvent after dehydration by azeotropic distillation is preferably not more than 55 percent by weight, more preferably 25 to 55 percent by weight as nonvolatile content.
The surface-treatment with the silane coupling agent can be proceeded by mixing the silane coupling agent with the dispersing component of the inorganic oxide sol dispersed in the azeotropic solvent after the dehydration by azeotropic distillation. The temperature of surface-treatment with the silane coupling agent is particularly not limited, preferably 20 to 100xc2x0 C., more preferably 30 to 90xc2x0 C., furthermore 40 to 80xc2x0 C.
The water content of the inorganic oxide sol dispersed in the azeotropic solvent after the surface-treatment with the silane coupling agent is generally preferably not more than 1 percent by weight, more preferably not more than 0.5 percent by weight.
The solvent of inorganic oxide sol dispersed in the azeotropic solvent can be substituted with the desired solvent according to the need. The solvents used in solvent substitution include an alcohol described above, acetone, methylethylketone, methylisobutylketone, cyclohexanone, dimethylacetoamide and dimethylformamide. The solvent substitution is proceeded in the range of preferably 30 to 120xc2x0 C., more preferably 40 to 110xc2x0 C., though it is influenced by the kind of the solvents.
In the coating composition of the present invention, the dispersing components of inorganic oxide sol may be utilized singly or as a combination of two or more members. The amount of the nonvolatile matter of the dispersing component of inorganic oxide sol is selected to be 5 to 60 percent by weight based on the total amount of nonvolatile matter of ingredient (A), ingredient (B) and ingredient (C). When the amount of the nonvolatile matter of the dispersing component of inorganic oxide sol is less than 5 percent by weight to the total amount of nonvolatile matter, the effect of addition of the dispersing component of inorganic oxide sol is not sufficiently obtained and the improvement effect of the stain resistance, stain-removing property and weathering resistance of the paint film is not sufficiently obtained. When the amount of the nonvolatile matter of the dispersing component of inorganic oxide sol is more than 60 percent by weight to the total amount of nonvolatile matter, the trend of the decrease in the flexibility of the paint film is observed. The amount of the nonvolatile matter of the dispersing component of inorganic oxide sol is preferably 5 to 40 percent by weight against the total amount of nonvolatile matter in view of the balance of stain resistance, stain-removing property, weathering resistance, and flexibility of the paint film.
The average particle diameter of the dispersing component of inorganic oxide sol is preferably not more than 100 nm, more preferably not more than 50 nm. When the average particle diameter is more than 100 nm, transparency of a clear film decreases and the stain resistance and removing property of the paint film decrease.
In the coating composition of the present invention, a curing reaction catalyst may be utilized. When the polyisocyanate compound having two or more isocyanate groups and/or blocked isocyanate groups in the molecule is used as ingredient (B) in the coating composition of the present invention, the curing reaction catalysts include a tin compound and a zinc compound. The tin compounds include tin halides such as tin chloride and tin bromide; organic tin compounds such as dibutyltindiacetate and dibutyltindilaurate. The zinc compounds include zinc halides such as zinc chloride and zinc bromide; organic acid zinc salts such as zinc octanoate and zinclaurate. The tin compound and the zinc compound of the curing reaction catalyst may be utilized singly or as a combination of two or more members and may be utilized together with other curing reaction catalysts. The preferable amount of the curing reaction catalyst is 0.01 to 5 percent by weight based on the total amount of nonvolatile matter in the coating composition. When the amount of the curing reaction catalyst is less than 0.01 percent by weight, the promoting effect of the curing reaction may be insufficiently exerted. When the amount of the curing reaction catalyst is more than 5 percent by weight, the water resistance and moisture resistance of the paint film may be decreased, and the decreases of the stain resistance, removing resistance and weathering resistance of the paint film may be caused. The more preferable amount of the curing reaction catalyst is 0.01 to 2 percent by weight based on the total amount of nonvolatile matter of the composition in view of the balance of the curing rate and the properties of the paint film.
In the coating composition of the present invention, when the aminoplast resin is used as ingredient (B), a curing reaction catalyst for the aminoplast resin may be utilized. The curing reaction catalysts for the aminoplast resin include phosphoric acid curing catalyst, sulfonic acid curing catalysts such as toluenesulfonic acid and dodecylbenzenesulfonic acid, and the amine-blocked compound thereof. The curing reaction catalysts may be utilized singly or as a combination of two or more members and may be utilized together with other curing reaction catalysts in order to control the curing time. The preferable addition amount of the curing reaction catalyst for the aminoplast resin is 0.01 to 2 percent by weight based on the total amount of nonvolatile matter of the coating composition. With respect to the reason, when the amount of the curing reaction catalyst is less than 0.01 percent by weight, the effect of the curing reaction catalyst for the aminoplast resin may be not manifested in curing of the coating composition. When the amount of the curing reaction catalyst is more than 2 percent by weight, the properties such as water resistance and moisture resistance of the paint film may become bad by the influence of the curing reaction catalyst after forming the paint film and the stain resistance, removing properties of stain and weathering resistance of the paint film may be decreased.
When an enamel is produced by compounding the proper pigments, dyes or flake pigments (brightener) in preparing the composition of the present invention, the obtained enamel does not lose the essential effect. Therefore, it is possible to give design properties such as the coloration of the substrate by compounding colored pigments other than a clear coating composition. It is also possible to control the properties of the paint film by compounding an extender pigment. These include colored pigments such as titanium oxide, carbon black, an organic pigment and red iron oxide; colorant such a as glass flake, aluminum flake and mica flake; fillers such as talc; and extender pigments such as strontium chlomate and barium sulfate.
When the coating composition of the present invention contains the pigment, the amount of the pigment is generally preferably 0.1 to 40 percent by weight, more preferably 0.5 to 35 percent by weight.
The preparation methods of the coating composition of the present invention are not particularly limited and includes that of the mixing essential components and required various additives in an arbitrary order and with other various methods. The preferable preparation method is the following method.
That is the preparation method which is proceeded by using a organic-inorganic composite obtained by copolymerizing 10 to 90 percent by weight of (a) a (meth) acrylic acid ester of an alkyl alcohol of 1 to 12 carbon atoms, 10 to 50 percent by weight of (b) a polymerizable double bond-containing and hydroxyl group-containing monomer, 0.1 to 10 percent by weight of (c) a polymerizable double bond-containing and carboxyl group-containing monomer, 0 to 20 percent by weight of (d) styrene, 0 to 20 percent by weight of (e) acrylonitrile and 0 to 10 percent by weight of (f) other polymerizable double bond-containing monomer to produce a resin (A) having a glass transition temperature of 50 to 120xc2x0 C., a number average molecular weight of 2,000 to 100,000, a hydroxyl value of 50 to 150 mgKOH/g and an acid value of 1 to 25 mgKOH/g, and adding at least one (C) dispersing component of an inorganic oxide sol selected from the group consisting of an aluminum oxide sol, a silica sol, a zirconium oxide sol and an antimony oxide sol into a polymerization liquid to be 5 to 60 percent by weight as a nonvolatile matter of ingredient (C) based on a total amount of nonvolatile matter of ingredient (A), ingredient (B) and ingredient (C) after finishing of the copolymerization of the resin (A), or by mixing and stabilizing ingredient (C) in the monomers and by copolymerizing the monomers. Particularly, after finishing of the copolymerization to obtain the resin of ingredient (A), the dispersing component of the inorganic oxide sol of ingredient (C) is preferable to be added into the polymerization liquid under heating or without heating and to be stabilized in dispersion state.
The addition of a diluent is generally conducted to control the concentration of the resin liquid after the preparation of the resin of ingredient (A) by polymerization. The addition of the dispersing component of the inorganic oxide sol of ingredient (C) is replaced to the addition of the diluent.
By adding the dispersing component of the inorganic oxide sol into the polymerization liquid after finishing of the copolymerization of the resin of ingredient (A), it is difficult to cause the aggregation of the dispersing component of the inorganic oxide sol. And, in the case of the further addition of the dispersing component of the inorganic oxide sol at later stages, it is difficult to cause the aggregation of the dispersing component of the inorganic oxide sol.
In the application of the coating composition, the operation efficiency of electrostatic coating, transfer efficiency of coating, atomization of particulate and appearance of the paint film are extremely improved. Therefore,the operation efficiency in coating process line is extremely improved and the appearance of the obtained paint film is very superior. Further, when the concentration of the organic-inorganic composite solution, in which the ingredient (C) is dispersed and stabilized, is increased, rise of viscosity is comparably low and high solid coating composition can be easily obtained. The coating composition of the present invention is preferable as a coating composition capable to decrease environmental pollution.
As described above, the preferable addition of the dispersing component of the inorganic oxide sol of ingredient (C) is conducted after finishing of the copolymerization of the resin of ingredient (A). The term xe2x80x9cafter finishing of the copolymerizationxe2x80x9d means xe2x80x9cafter preparation of the resin of ingredient (A) having a glass transition temperature of 50 to 120xc2x0 C., a number average molecular weight of 2,000 to 100,000, a hydroxyl value of 50 to 150 mgKOH/g and an acid value of 1 to 25 mgKOH/gxe2x80x9d. The polymerization liquid may contain unreacted monomers.
The addition of the dispersing component of the inorganic oxide sol of ingredient (C) is preferably conducted at the temperature of not more than the boiling point of the dispersion medium of the inorganic oxide sol of ingredient (C), more preferably conducted at the temperature of 10 to 50xc2x0 C. lower than the boiling point of the medium of the inorganic oxide sol of ingredient (C). The polymerization liquid before the addition of the dispersing component (C) contains preferably 40 to 80 percent by weight, more preferably 50 to 70 percent by weight of the resin material.
In the case of the clear coating composition, preferable preparation methods of the coating composition include a preparation method comprising mixing and stabilizing the dispersing component of the inorganic oxide sol of ingredient (C) in the solvents of polymerization and then copolymerizing the monomers to produce the resin of ingredient (A) in the same condition described above and uniformly mixing the resin (A) according to the need, the curing agent of ingredient (B) and required various additives, and a preparation method comprising copolymerizing the monomers to produce the resin of ingredient (A) and then adding and stabilizing the dispersing component of the inorganic oxide sol in the polymerization liquid under heating or without heating to produce the organic-inorganic composite solution, in which the inorganic oxide sol is dispersed and stabilized, and uniformly mixing the resin (A) according to the need, the curing agent of ingredient (B) and required various additives.
In the case of the enamel coating composition, the coating composition of this invention can be prepared by dispersing the desired pigment together with the resin of ingredient (A) and/or a dispersant and the like by a dispersing machine and compounding it in the clear coating composition described above. The various additives used according to the need include colorants such as a dye, a glass flake, an aluminum flake and mica flake, a filler, a solvent, a pigment dispersant, a flow controlling agent, a leveling agent, an antigelling agent, an antioxidant, an ultraviolet absorber, an ultraviolet stabilizer and a radical scavenger.
The curing temperature and time required to curing such coating compositions of the present invention are influenced with the kind of the ingredients and the reaction catalysts, the curing temperature is generally a room temperature to 220xc2x0 C. and the curing time is generally 30 seconds to 10 hours.
The coating compositions of the present invention can be utilized in a single layer paint film or in multi layers paint film.
The multi layers paint films include that prepared by the coating method comprising applying a colored film forming composition on a substrate to form a base coat film and then applying a clear coat film forming composition of the this coating composition on the base coat film to form a clear top coat film.
The colored film forming composition of the base coat film comprises a resin binder and a pigment. The resin binders include various binders such as a conventional acrylic resin, a polyester resin (containing an alkyd resin), a polyurethane resin and melamine resin.
The colored film forming composition of the base coat film can comprise at least one of conventional various additives such as a surface active agent, a leveling agent, a thixotropic agent, a filler, a defoaming agent, an organic solvent and a catalyst.
The amount of the pigment is preferably 1 to 80 percent by weight, more preferably 3 to 60 percent by weight in the colored film forming composition.
The pigments include various pigments of organic pigments and inorganic pigments. Examples of the pigments include surface treated metallic pigments such as aluminum, copper, brass, bronze, stainless steel, iron oxides of mica form, metallic powders of flake form and mica coated with titanium dioxide or iron oxides; inorganic pigments such as titanium dioxide, iron oxides, yellow iron oxide and carbon black; organic pigments such as phthalocyanine blue, phthalocyanine green and quinacridone red pigments; extender pigments such as precipitated barium sulfate, clay, silica and talc.
The method of applying the coating composition to form the multi layers paint film includes a method which comprises heating the colored film forming composition of the base coat film or controlling the viscosity by adding organic solvents or reactive diluents according to the needs, and applying the colored film forming composition on the substrate by conventional coating machines such as air spray, electrostatic air spray, roll coater, flow coater, dip type coating machine and the like, brush, bar coater or applicator in an amount to form a film having dried thickness of 0.5 to 300 xcexcm and curing, in general, in the condition of 50 to 300xc2x0 C. for 5 seconds to 24 hours, followed applying the clear forming composition of the clear coat film on the base coat by the above method in an amount to form a film having dried thickness of 10 to 100 xcexcm, preferable 10 to 60 xcexcm and curing, in general, in the condition of 50 to 300 xc2x0 C. for 5 seconds to 24 hours and the like and a method which comprises, in the case of two coat one bake coating, diluting the colored film forming composition with suitable solvents such as organic solvents to control the desirable viscosity, applying the base coat composition on the substrate by the above method in an amount to form a film having dried thickness of 5 to 40 xcexcm, preferable 7 to 35 xcexcm, allowing to stand at room temperature to 100 xc2x0 C. for 1 to 20 minutes, followed applying the clear forming composition of the clear coat film on the base coat by the above method in an amount to form a film having dried thickness of 10 to 100 xcexcm, preferable 10 to 60 xcexcm and curing, in general, in the condition of 50 to 300xc2x0 C. for 5 seconds to 24 hours and the like. Preferable method of the application is the application by an air spray in the above methods.
Other multi layers paint film includes that produced by a method which comprises applying a colored base coating composition on the substrate, followed by applying a clear coating composition on the uncured colored base coat and curing the coats, and then by applying an over clear coating composition on the clear coat and curing, wherein the clear coating composition is an acrylic resin-aminoplast resin coating composition and the over clear coating composition is the coating composition of this invention. The colored base coating composition is similar to that described in the above multi layers paint film.
The acrylic resin-aminoplast resin coating composition can be used as the clear coating composition applied on the uncured colored base coat. The acrylic resins include a resin produced by copolymerizing (a) a (meth) acrylic acid ester of an alkyl alcohol of 1 to 12 carbon atoms, (b) a polymerizable double bond-containing and hydroxyl group-containing monomer and (c) a polymerizable double bond-containing and carboxyl group-containing monomer, and optionally (d) styrene, (e) acrylonitrile and (f) other polymerizable double bond-containing monomer and the like. The preferable aminoplast resins include a melamine resin and a guanamine resin. The aminoplast resin may be utilized singly or in a combination of two or more members. The aminoplast resin has two or more reactive groups in the molecule and is not particularly limited. The triazin ring may be one or more in a molecule of the melamine resin and the guanamine resin. The preferable reactive group in the resins includes methylol group, imino group and groups etherificated with methanol or butanol. The compound ratio of the acrylic resin and the aminoplast resin in the acrylic resin-aminoplast resin coating composition is not particularly limited and preferably 90: 10 to 50: 50, more preferably 80: 20 to 60: 40 in parts by weight.
A curing reaction catalyst for the aminoplast resin can be formulated in the acrylic resin-aminoplast resin coating composition. Preferable examples of the curing reaction catalysts for the aminoplast resin are , for example, a phosphoric acid curing catalyst, sulfonic acid curing agents such as toluenesulfonic acid and dodecylbenzenesulfonic acid and an amine blocked compound thereof. The curing reaction catalysts can be utilized singly or in combination of two or more members and may be utilized together with other compounds in order to control the curing time. The additional amount of curing reaction catalyst is preferably 0.01 to 2 percent by weight based on the total amount of nonvolatile matter in the acrylic resin-aminoplast resin coating composition.
The clear coating composition in the method of preparing the multi layers paint film can comprise additives such as a flow controlling agent, a leveling agent, an antigelling agent, an antioxidant, an ultraviolet absorber, an ultraviolet stabilizer and a iradical scavenger, according to the needs.
The preferable methods of preparing the multi layers paint film include a method which comprises controlling the viscosity by heating the colored film forming composition of the base coat film or adding organic solvents or reactive diluents according to the needs, and applying the colored film forming composition on the substrate by conventional coating machines such as air spray, electrostatic air spray, roll coater, flow coater, dip type coating machine and the like, brush, bar coater or applicator in the amount to form a film having dried thickness of 5 to 40 xcexcm, preferably 7 to 35 xcexcm and allowing to stand , in general, in the condition of a room temperature to 100 C. for 1 to 20 minutes, followed applying the clear coating composition on the base coat by the above method in the amount to form a film having dried thickness of 10 to 100 xcexcm, preferable 10 to 60 xcexcm and curing, in general, in the condition of 50 to 300xc2x0 C. for 5 seconds to 24 hours and the like and then applying the over clear coating composition on the clear coat by the above method in the amount to form a film having dried thickness of 5 to 50 xcexcm, preferable 5 to 20 xcexcm and then curing, in general, in the condition of 50 to 300xc2x0 C. for 5 seconds to 24 hours.
The kind of the substrate to which the coating is applied is not particularly limited, but various kinds of organic or inorganic substrate materials, such as woods, glasses, metals, fabrics, plastics, rug foamed articles, elastomers, papers, ceramics, concretes and gypsum boards, may be utilized. The substrates may be treated on the surface and coated with one or more coating compositions.
Coated articles prepared by the coating composition of the present invention include buildings, structures, wood articles, metallic articles, plastics articles, rubber articles, finished papers, ceramic articles and glass articles, specifically automobiles, parts for automobiles (for example, body, bumper, spoiler, mirror, wheel such as aluminum wheel and inner package material, and these parts are made of various materials), metal plates such as steel plates, two-wheel barrows, parts for two-wheel barrows, materials for road (for example, steel rail and traffic control sign), materials for tunnel (for example, sidewall plate), marine vessels, railway vehicles, airplanes, printing machines, parts for printing machines, furnitures, musical instruments, house-hold electric instruments, building materials, vessels, office articles, sport articles and toys.
The coating composition of the invention can be utilized in an ink, an adhesive agent and a mold except for the coating composition.